Free-exciton magnetoreflectance and magnetization are used to study the p-d exchange interaction of Cd 1Ϫx Cr x S ͑xϭ0.0024, 0.0031, and 0.0033͒. Magnetization data are well described by a simple crystal-field model taking into account static, tetragonal Jahn-Teller distortion suffered by Cr 2ϩ ions, as well as the hexagonal crystal field of CdS. In effect, a strong magnetic anisotropy of a single Cr 2ϩ ion was found. From the heavy-hole exciton splitting, and the Cr 2ϩ ion spin deduced from magnetization data, the p-d exchange parameter was evaluated as N 0 ␤ϭϩ0.48Ϯ0.05 eV, using the previously obtained s-d exchange parameter: N 0 ␣ϭϩ0.22Ϯ0.01 eV. These exchange parameters provide a reasonable description of the exciton splittings for a magnetic field oriented along or perpendicularly to the crystal hexagonal axis.

The theory of a donor bound magnetic polaron ͑BMP͒ in Cr-based diluted magnetic semiconductors is presented. The Cr BMP generalizes the physical situation for Mn-based and Fe-based BMP due to particular energy structure of Cr 2ϩ ions, exhibiting features typical for both Mn 2ϩ and Fe 2ϩ ions. The ground state of the Cr 2ϩ ion is a semidoublet, yielding a permanent magnetic moment of the ion, similarly as for Mn 2ϩ or Co 2ϩ ions. On the other hand the ground state is followed by closely lying excited states, analogously to the situation for Fe 2ϩ ions. The developed Cr BMP model recovers characteristic behavior of both Mn BMP and Fe BMP: zero-field spin-flip energy ͑a fingerprint of Mn BMP͒ and anticrossings of BMP states ͑typical for Fe BMP͒. The model provides a perfect description of the BMP energy structure recently observed in a spin-flip Raman scattering experiment of Cd 1Ϫx Cr x S. Additionally, from this analysis the Cd 1Ϫx Cr x S conduction band exchange integral is evaluated as N 0 ␣ϭϩ0.22 eV. ͓S0163-1829͑98͒02435-7͔

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The exciton splitting induced by the s-d and p-d exchange interaction in Zn 1Ϫx Fe x Te (xϽ0.005) was studied by polarized magnetoreflectance. Data were taken at 2 K in magnetic fields up to 5 T. Combining these results with magnetization data, a value (N 0 ␣ϪN 0 ␤) ϭ 2.1Ϯ0.4 eV was obtained for the difference between the s-d and p-d exchange constants. Assuming that N 0 ␣ϭϩ0.2 eV, the p-d exchange is antiferromagnetic, with a magnitude N 0 ␤ϭϪ1.9 eV.

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